text: This variant keeps the membrane unit outside of the main reactor unit, hence its name. In this configuration, the wastewater goes through the anaerobic process. After this step is complete, the remaining mixed liquor, put under a high amount of pressure, flows into the external membrane unit. Keeping the same pressure, crossflow filtration is utilized to separate the permeate and retentate, effluent and organic load respectively. Ultimately, the two end up settling on opposite sides of the membrane filtration system. From here, the effluent is released and the organic load cycles back to the main reactor unit where it can go through the anaerobic process to create more biogas.